First Pass Yield (FPY)
First Pass Yield measures the percentage of units that pass through a process correctly the first time, without any rework, repair, or rejection. It reveals the true quality of a process.
First Pass Yield (FPY) answers a critical question: What percentage of production gets it right the first time? Unlike final yield (which includes reworked parts), FPY exposes all the hidden rework loops that consume time and resources without adding value.
FPY is calculated per process step: FPY = Good units (without rework) / Total units entering the step. For a multi-step process, Rolled Throughput Yield (RTY) is the product of all individual FPYs -- and the number is often shockingly low.
A process with 95% FPY at each of 5 steps has an RTY of only 77.4% (0.95^5). This means nearly 1 in 4 units requires rework somewhere in the process. Traditional yield metrics hide this because they count reworked parts as 'good' at the end.
Improving FPY directly reduces cost, lead time, and capacity waste. Every unit that needs rework consumes double the resources: Once to make it wrong, once to fix it. Eliminating rework is often the fastest path to increased effective capacity.
Formula
FPY = Units passing without rework or defect / Total units entering the process. RTY = FPY1 x FPY2 x ... x FPYn
Practical Example
An assembly line has 4 stations. Station FPYs: 97%, 94%, 98%, 96%. RTY = 0.97 x 0.94 x 0.98 x 0.96 = 85.8%. Although each station looks good individually, 14.2% of all units require rework somewhere. At 1,000 units/day, that is 142 rework events daily -- a massive hidden cost.
How Leanshift Helps
Leanshift tracks process outcomes at each station, enabling FPY calculation per step and RTY across the entire process. This visibility reveals exactly which steps generate the most rework, guiding targeted quality improvement.
Frequently Asked Questions
What is the difference between FPY and final yield?
Final yield counts all units that eventually pass -- including those that were reworked. FPY only counts units that passed correctly the first time. Final yield hides rework; FPY exposes it.
What is a good FPY?
It depends on the industry. Electronics assembly: >98%. Automotive: >95%. Machining: >97%. More important than the absolute number is the trend and the gap between FPY and 100% -- that gap represents improvement potential.
How do you improve FPY?
Identify the top defect types per station (Pareto analysis), find root causes (5-Why, Ishikawa), implement countermeasures (Poka-Yoke, Standard Work), and verify with ongoing measurement. Attack the lowest-FPY station first for maximum impact.
Related Terms
OEE (Overall Equipment Effectiveness)
OEE is the key metric for machine and equipment productivity. It combines availability, performance, and quality into a single percentage value.
Poka-Yoke (Error Proofing)
Poka-Yoke is a design approach that makes errors impossible or immediately detectable. It builds quality into the process rather than relying on inspection after the fact.
Scrap Rate / Rejection Rate
Scrap rate measures the percentage of production that is irreparably defective and must be discarded. It directly impacts material cost, OEE quality factor, and environmental waste.